cd50.iso is an ISO9660 image that can be used to create a bootable CD with most popular CD-ROM creation software on most platforms. This image has the widest selection of drivers, and is usually the recommended choice if your hardware can boot from a CDROM.

cdemu50.isois an ISO9660 image, using "floppy emulation" booting, using a 2.88M floppy image. It is hoped that few people will need this image -- most people will use cd50.iso, only use cdemu50.iso if cd50.iso doesn't work for you.